Overview
ISO 21736:2020 - Refractories - Test methods for thermal shock resistance specifies standardized procedures to evaluate how refractory materials withstand rapid temperature changes. The document defines the principle, required equipment, test-piece preparation, step-by-step procedures, expression of results and reporting for three distinct thermal‑shock test methods. Each method targets different product types and test results are not directly comparable. Test conditions (method, temperature, cycle parameters) are to be agreed between contracting parties.
Key topics and technical requirements
- Three test methods:
- Method 1: water quenching - rapid immersion in flowing water (5 °C to 35 °C). Applicable to dense aluminium‑silicate refractories but excludes basic, silica, fused‑cast products, highly porous (>45 %) materials or those that react with water.
- Method 2: compressed air quenching - rapid quenching in 0.1 MPa compressed air at ambient temperature.
- Method 3: air quenching - quenching in natural ambient air.
- Principle: fast heating followed by rapid cooling; damage on the hot end surface is used to describe thermal‑shock resistance.
- Equipment & control:
- Electric furnace with uniform temperature zone (Δ ≤ 10 °C across hot surface).
- Thermocouple placement (sealed, ~20 mm ± 5 mm from hot end surface).
- Cooling channel or compressed‑air delivery and test‑piece clamps.
- Drying oven for preconditioning (110 °C ± 5 °C).
- Test pieces: standard brick dimensions (230 × 114 × 64 (74) mm) or negotiated alternatives; monolithic specimens prepared per referenced sampling/preparation standards.
- Procedure specifics:
- Pre‑dry to constant mass; rapid transfer to furnace, allow temperature recovery (furnace drop ≤ 50 °C; recover to test temperature within 5 min), hold time (e.g., 20 min after regaining temperature).
- For water quench, immerse 50 mm ± 5 mm of hot end; manage flow so inflow/outflow temp rise ≤ 10 °C.
- Results & reporting: damage assessment grids, expression of results, and required report contents are specified; precision data provided in Annex A.
- Safety: the standard does not cover all safety issues - users must establish appropriate safety and regulatory practices.
Applications
ISO 21736:2020 is used for:
- Quality control and acceptance testing of shaped and monolithic refractories.
- Material selection and comparative evaluation within the same method/product class.
- R&D and lifecycle assessment for refractory linings in furnaces, kilns, boilers and industrial processes subject to thermal cycling.
- Contract specification between manufacturers, buyers and testing laboratories.
Who will use it: refractory manufacturers, independent testing laboratories, R&D engineers, plant metallurgists, procurement/specification writers, and certification bodies.
Related standards
- ISO 836 - Terminology for refractories
- ISO 1927-2, ISO 1927-5 - Sampling and test‑piece preparation for monolithic refractories
- ISO 5014 - Modulus of rupture at ambient temperature
- ISO 5022 - Sampling and acceptance for shaped refractories
Keywords: ISO 21736:2020, thermal shock resistance, refractories testing, water quench test, compressed air quench, air quench, refractory quality control, thermal‑shock methods.
